Image forming apparatus

ABSTRACT

If an edge of a sheet metal of a image forming apparatus damages an electric cable, the image signal is distorted and no correct image is formed since the damage causes feeding failure and signal deterioration. This is remarkable in the conventional digital electrophotographic apparatus, since the drive signal to drive a laser or a light emitting diode (LED) for exposing the photosensitive body becomes higher in frequency as a resolution and speed are increased and tends to generate the electric noise. In order to prevent damage of an electric cable by a metal frame, an apparatus having a holder for holding a feed cable is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus such as acopying machine, facsimile apparatus and the like.

2. Related Background Art

In general, an image forming apparatus of an electrophotographic systemforms an electrostatic latent image by exposing a charged photosensitivebody to an image light, and after this electrostatic latent image isdeveloped, it is transferred on a recording medium such as a paper orthe like.

In such an image forming apparatus, an electric cable is used forfeeding and transmitting a signal, and the cable is usually fixed to asheet metal frame of the apparatus body.

As miniaturization of the apparatus has been progressing, restrictionhas come to be imposed on a wiring position and fixing position of thecable and sometimes the cable may come into contact with an edge of themetal frame.

In this case, since the edge of the sheet metal frame is sharp, theelectric cable may be damaged, thereby causing feeding failure andsignal deterioration.

Hence, a resin block is attached to the frame and the cable is fixed tothis resin block, so that the cable can be prevented from contacting theedge.

However, since the resin block has an electric non-conductance, therearose a problem that an electric noise is generated when the cabletransmits a high frequency.

Particularly, in a digital electrophotographic apparatus, the drivesignal to drive a laser or a light emitting diode (LED) for exposing thephotosensitive body becomes higher in frequency as a resolution andspeed are increased and tends to generate the electric noise.

When this noise is superposed on an image signal, the image signal isdistorted and an incorrect image is formed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image formingapparatus which prevents the damage of an electric cable by a metalframe.

Another object of the present invention is to provide an image formingapparatus in which the electric cable can be installed.

Yet another object of the present invention is to provide an imageforming apparatus as described in the claims.

Yet further objects of the present invention will be apparent from thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a schematic configuration of animage forming apparatus according to an embodiment of the presentinvention;

FIG. 2 is a view showing a wiring of a feed cable provided for the imageforming apparatus;

FIG. 3 is a schematic view of a holder of the embodiment of the presentinvention;

FIGS. 4A, 4B and 4C are explanatory views explaining the configurationof the holder of the embodiment of the present invention;

FIG. 5 is an explanatory view explaining the wiring of the conventionalfeed cable;

FIGS. 6A and 6B are explanatory views explaining a method of holding thefeed cable; and

FIG. 7 is a prototype of an electric non-conductance resin holder builtby the present inventor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail below with referenceto the drawings.

First, an embodiment of the present invention will be described.

In the first place, an image forming process in the image formingapparatus adapting the electrophotographic system which is one exampleof the image forming apparatus according to the present embodiment willbe explained with reference to FIG. 1.

In such an image forming apparatus, as shown in FIG. 1, first, second,third and fourth image forming sections Pa, Pb, Pc and Pd, which formimages of respective colors of yellow, magenta, cyan and black, areinstalled. The image forming sections Pa, Pb, Pc and Pd comprisephotosensitive drums 17 a to 17 d which are image bearing bodiesrespectively, and on which, after being evenly charged by charging means18 a to 18 d, electrostatic latent images are formed by electrostaticlatent image forming means 19 a to 19 d which use the light emittingdiode as an exposure light source. After that, the electrostatic latentimages are developed by the toners of various colors by developing means20 to 20 d, and the toner images are electrostatically transferred on arecording medium by transfer means 21 a to 21 d and then the tonerimages are fixed on the recording medium by heat and pressure of fixingmeans 12.

Under the above described first, second, third and fourth image formingsections Pa, Pb, Pc and Pd from a cassette 11 which stores recordingpapers as the recording medium to the fixing apparatus 12, a recordingpaper conveying belt as recording paper conveying means (hereinaftersimply referred to as conveying belt) 13 in the shape of an endless beltwhich circularly moves through these image forming sections to conveythe recording papers is installed.

The conveying belt 13 is a belt endlessly driven in the directionindicated by an arrow A by a drive roller 14 and bears the recordingpapers which are supplied from the cassette 11 and synchronized by apair of registration rollers 15 and fed and conveyed in order to theabove described image forming sections Pa, Pb, Pc and Pd.

The fixing apparatus 12 receives the recording paper discharged from thedrive roller 14 side and collectively fixes the toner images of eachcolor, which are superposed and transferred on the recording paper inthe image forming sections Pa, Pb, Pc and Pd, on the above describedrecording paper and forms a permanent image, and thereafter dischargesthe above described recording paper to a discharge tray 16.

A control line for electrically controlling the photosensitive drums 17a to d and the electrostatic latent image forming means 19 a to d andthe like of the above described image forming sections Pa, Pb, Pc and Pdand a feed cable 24 which is a power source line for supplying anelectric power to the image forming sections Pa, Pb, Pc and Pd finallyreach, as shown in FIG. 2, the power source (not shown) and a controlsubstrate 22 through the metal frame. These power source and controlsubstrate 22 are usually installed at the rear of the apparatus. In thevicinity of the image forming sections, driving sources 23 a and 23 bare installed respectively. In the case where these driving sources 23 aand 23 b avoid the metal frame 21 and try to secure a passage for thefeed cable 24, a wiring passage inevitably becomes long. Particularly inthe case of the present embodiment such as the image forming apparatuscomprising four image forming sections, the installation of the feedcable 24 is complicated. In order to make the wiring passage of the feedcable 24 the shortest, it is desirable to take out the feed cable 24from the position close to the rear of the metal frame 21 in the imageforming sections.

However, if the feed cable 24 is attached to the metal frame 21 as itis, the edge of the metal frame 21 inflicts damage to the feed cable 24.

Therefore, the present inventor attached a holder 205 (FIG. 7) made ofelectric non-conductance resin to the metal frame 201, which protectsand holds the feed cable 204. Nevertheless, since the feed cable 204 hasbeen transmitting high frequency electric signals, electric noises wereproduced, which were superposed on the high frequency electric signals,thereby disturbing the images.

In view of the above, the present inventor has attached, as shown inFIG. 3, a holder 30 comprising a substrate 25 made of resin and anelectro-conductive sheet 28 to the metal frame 21.

The electro-conductive sheet 28, as shown in FIG. 3 and FIG. 4A, isinstalled in such a manner as to go around from the side of the holder30 to which the feed cable 24 is held to the side of the holder 30 thatthe metal frame 21 is contacted through a feed cable pressing member 29.In this manner, the feed cable 24 held by the holder 30 can beelectrically connected to the metal frame 21.

When constituted in such a manner, the feed cable 24 is not brought intocontact with the metal frame 21 and therefore is not damaged by the edgeof the metal frame 21. Further, since the feed cable 24 is grounded tothe metal frame 21 through the electro-conductive sheet 28, the electricnoises are removed and have no influence on the images. Furthermore,being made of resin, the substrate can be obtained in a desired shapeand is inexpensive, compared to being made of metal.

Here, a method of holding the feed cable 24 in the image formingapparatus according to the present embodiment will be described.

Between a gap d2 of the feed cable pressing member 29 of the holder 30and a line diameter d1 of the feed cable 24, there exists a relationshipof d2<d1 as shown in FIG. 4B and therefore, in a state in which the feedcable 24 is fitted with the pressing member 29, the feed cable 24 ispressed against the electro-conductive sheet 28. As a result, an earthcan be securely taken between the feed cable 24 and the metal frame 21through the electro-conductive sheet 28.

The electro-conductive sheet 28 is, as shown in FIG. 4C, divided intoplural layers.

As an example of the layers constituting the electro-conductive sheet28, a first combination can be enumerated as follows:

A first layer . . . a surface electro-conductive layer,

A second layer . . . an adhesive layer.

Or a second combination as follows:

A first layer . . . a surface electro-conductive layer,

A second layer . . . a resin layer.

Or a third combination as follows:

A first layer . . . a surface electro-conductive layer,

A second layer . . . a resin layer,

A third layer . . . an adhesive layer.

Having the adhesive layer is much easier in attaching theelectro-conductive sheet 28 to the substrate 25 of the holder 30 andexcellent in working performance. Having the resin layer reinforces theelectro-conductive layer 28 and makes it easy to handle. Note that theelectro-conductive sheet 28 made of any combination of the abovedescribed layers can be realized at relatively low cost. Further, incase of abolishing the image forming apparatus, removal of the sheetportion only of the holder 30 allows the remaining resin substrate 25 tobe utilized once again. At this time, if the electro-conductive sheet 28is installed in the resin substrate 25 in such a manner as to be easilypeeled off, it can be more easily utilized.

Incidentally, in the present embodiment, for the sake of simplicity, alocation of the holder 30 is limited, but the location is essentiallynot to be limited. Further, in the present embodiment, though the imageforming apparatus comprising four image forming sections was employed,it is not limited to this configuration. Further, in the presentembodiment, though lead wires of the image forming means are connectedto the power source or the substrate, the connecting point is notlimited to this.

The foregoing embodiments are included merely to aid in theunderstanding of the invention. However, it is to be understood that theinvention is not intended to be limited to the embodiments, andvariations may be made by skilled in the art without departing from thespirit and the scope of the invention.

1. An image forming apparatus that forms an image on a recordingmaterial, said image forming apparatus comprising: an electrical board;a unit, provided at a portion spaced from said electrical board,receiving current from said electrical board; an electrical cable whichelectrically connects between said electrical board and said unit,wherein a surface of said electrical cable is insulated; and anelectrical cable holder having a resin member, a conductive sheetprovided on the resin member and grounded, and a cable supporting memberwhich supports said electrical cable to contact the surface of saidelectrical cable with the conductive sheet, wherein said unit is an LEDarray which illuminates a light beam according to an image formingsignal transmitted from said electrical board to the LED array with saidelectrical cable.
 2. An image forming apparatus according to claim 1,wherein the electrical cable supporting member is integral with saidelectrical cable holder.
 3. An image forming apparatus according toclaim 1, wherein the resin member is grounded through a metal member ofsaid image forming apparatus.
 4. An image forming apparatus according toclaim 1, wherein the electrical conductive sheet is removable from theresin member.
 5. An image forming apparatus according to claim 1,wherein a high frequency electrical signal is transmitted to said unitwith said electrical cable.
 6. An image forming apparatus according toclaim 1, wherein said electrical cable holder includes a plurality ofelectrical cable supporting members.
 7. An image forming apparatusaccording to claim 1, wherein said electrical cable holder is capable ofsupporting a plurality of electrical cables.